Neoplasia of the Maxilla and Mandible

Chapter 99 Neoplasia of the Maxilla and Mandible



Matthew Palmisano



ETIOLOGY


The oropharyngeal region is the fourth most common site of malignant neoplasia in the dog.




Key Point


The most common oral neoplasms in the dog are malignant melanoma, squamous cell carcinoma (SCC), fibrosarcoma, and epulides. In the cat, SCC in the most common oropharyngeal cancer, followed by fibrosarcoma.


Malignant melanoma and epulides occur rarely in the cat. Odontogenic tumors are the most common benign tumor in the cat. Oral tumors tend to be locally aggressive and have a low metastatic rate, except for malignant melanoma, caudal tongue tumors, and tonsillar SCC.


Certain breeds of dogs appear to be predisposed to oral tumors, including boxers, golden retrievers, and cocker spaniels. Small-breed dogs have a greater tendency to develop malignant melanoma, and large-breed dogs are more prone to develop SCC and fibrosarcoma.


Morbidity and mortality often result from local disease rather than from distant metastasis. Therefore, local tumor control is paramount to a successful outcome. Surgical resection should be considered a first line of treatment for all oral neoplasms. See Table 99-1 for a summary of oral neoplasia in dogs and cats.



Table 99-1 SUMMARY OF COMMON ORAL CANCERS IN THE DOG AND CAT

image


DIAGNOSIS



History



• Most patients with oral neoplasms present with a chief complaint of drooling, halitosis, and dysphagia.

• Deformity of the muzzle also may be noticed by the owners.

• Oral tumors are often large, ulcerated, and painful, so patients may be anorexic.

• Oral bleeding may occasionally be seen, and some owners report seeing blood in the water dish after the pet drinks.

• Loose teeth or delayed healing after dental extraction may be observed. In the cat, teeth that are excessively loose and easily removed should lead to a suspicion of neoplasia, particularly SCC.


Physical Examination



• Physical examination may reveal palpable swelling of the muzzle or lower lip.

• Oral bleeding and halitosis are common clinical findings.

• If the tumor is associated with the temporomandibular joint (TMJ), vertical ramus of the mandible, or caudal pharyngeal region, pain may be elicited when trying to open the mouth.

• The mass may be smooth, ulcerated, or firm on oral examination and palpation.

• Many patients do not allow a complete oral examination while they are awake due to pain; consider sedation of patients.

• Since many oral neoplasms metastasize via the lymphatic system, palpate the submandibular and regional lymph nodes for enlargement.


Diagnostic Evaluation



Blood Tests



• Many of these patients are older (>8 years of age), so perform a minimum database (complete blood count, serum biochemical profile, urinalysis) to look for systemic illnesses related to the tumor or concurrent metabolic disorders.


Imaging Studies



• Obtain three-view chest radiographs to identify metastatic disease to the lungs.

• Obtain skull radiographs under anesthesia to evaluate the extent of bony involvement into the maxilla or mandible. A skull series (lateral, ventral-dorsal, right and left oblique views) is required to fully evaluate the skull (see Chapter 4). Radiographic abnormalities include changes in cortical bone density, periosteal new bone formation, involvement of adjacent soft tissues, and loose teeth.

• Computed tomography (CT) scanning and magnetic resonance imaging (MRI) of the skull is very helpful in evaluating extent of tumor invasion and presurgical planning. These imaging modalities are especially helpful in evaluating caudal maxillary tumors or tumors involving the orbit, zygoma, TMJ, or vertical ramus of the mandible.


Biopsy



• Perform an incisional biopsy before surgery to obtain a definitive diagnosis.



Key Point


Obtain a tissue biopsy of any suspicious oral lesions. Early detection is critical to successful treatment.



• Biopsy is very important in determining the treatment, as well as the long-term prognosis, for the pet. Many oral tumors do not exfoliate easily, so fine-needle aspiration is usually not helpful. A wedge biopsy for histopathologic examination is necessary for a definitive diagnosis.

• Obtain fine-needle aspirates for cytology or histopathologic evaluation via biopsy of all enlarged, submandibular, or pharyngeal lymph nodes to look for metastatic disease. Perform fine-needle aspiration even on normal-sized regional lymph nodes. In one study, 40% of dogs with oral melanoma had normal-sized lymph nodes and had evidence of metastasis to the lymph nodes on cytologic evaluation.


TUMOR TYPES



Benign Non-odontogenic Neoplasms



Epulis


Epulides are fibrous tumors originating from the periodontal ligament. They are rarely seen in the cat but are one of the most common oral tumors seen in the dog. There is no sex predisposition, and a familial predisposition has been noted in the boxer.


Three types of epulides are characterized, based on histopathologic evaluation:


• Fibromatous epulis is a benign, noninvasive growth in which the periodontal ligament stroma is the predominant cell type. These epulides are pedunculated and often multiple.

• Ossifying epulides have a similar biologic behavior to fibromatous epulides, but histopathologically they have an osteoid component. Malignant transformation to osteosarcoma has been reported.

• Acanthomatous epulis is the most aggressive of the epulides. This type of epulis is characterized by extensive bony invasion into the alveolar bone and is most often seen in the rostral mandible. Acanthomatous epulides can become quite large but do not metastasize. However, approximately 30% of acanthomatous epulides undergo malignant transformation.


Treatment and Prognosis



• Since epulides are local tumors, they can be treated with aggressive curettage of the alveolar socket (with fibromatous and ossifying epulides). However, a better outcome can be achieved with en bloc resection of the tumor and surrounding bone. En bloc resection is recommended with acanthomatous epulides due to their extensive bony involvement. Recurrence rate is high if the tumor is only debulked, and a complete resection is considered curative.

• Radiation therapy of epulides without surgery can be effective and is often curative. Large or incompletely excised epulides can be treated with surgery, followed by postoperative radiation therapy. Chemotherapy is generally not effective for epulides.


Other Benign Non-odontogenic Neoplasms


Other rarely seen, benign non-odontogenic neoplasms include fibroma, hemangioma, lipoma, chondroma, osteoma, and histiocytoma. These tumors look grossly similar and require biopsy for histopathologic evaluation.



Malignant Non-odontogenic Neoplasms



Malignant Melanoma


Malignant melanoma is characterized by local invasion and early metastasis. They can be darkly pigmented (melanotic) or non-pigmented (amelanotic). Oral melanomas are often ulcerated and necrotic, so clinical signs frequently seen are halitosis and oral bleeding. Dogs with more heavily pigmented oral mucosa, such as the chow, are predisposed to malignant melanoma. Malignant melanoma is found (in order of decreasing frequency) on the gingival, buccal and labial mucosa, hard palate, and tongue.



Treatment and Prognosis



• Treatment of choice is early, complete en bloc surgical resection. Tumor size is important, as melanomas less than 50 mm2 are associated with a better outcome.

• High-dose, fractionated radiation therapy has shown moderate success in treatment. One study showed an increase in survival time with surgery and radiation therapy when compared with surgery alone.

• Chemotherapy has not been effective to date in treatment of melanomas.

• Newer therapies, such as immunotherapy, have shown some promise in treatment.



Key Point


Overall prognosis with oral melanomas is poor, with a <10% 1-year survival even with treatment.



Squamous Cell Carcinoma


SCC is the second most common oral tumor in dogs, but it is the most common oral tumor in cats. SCC is characterized by local tissue invasion and late metastasis. SCC often looks ulcerative and friable on oral examination.


Two types of SCC are seen: non-tonsillar and tonsillar SCC. They have very different biologic behavior. Non-tonsillar SCC is locally invasive and slow to metastasize. SCC often invades bone, causing bony lysis and loosening of teeth. Tonsillar SCC is biologically very aggressive and is characterized by early metastasis to regional lymph nodes and lungs.



Treatment and Prognosis



• Wide surgical resection is the treatment of choice, with or without radiation therapy.

• Radiation therapy can be used as an adjunct for local control, especially with large tumors.

• The best long-term success can be achieved using surgical resection followed by postoperative radiation therapy.

• Chemotherapeutic agents, such as cisplatin and piroxicam, have been added to treatment protocols with some success.

• Overall prognosis is guarded. Local recurrence is high when the tumor is marginally resected, and approximately 50% of patients die within 1 year.


Fibrosarcoma



• Fibrosarcoma is the third most common tumor behind malignant melanoma and SCC, and it is the second most common tumor in cats.

• Fibrosarcomas are firm, slow-growing tumors that are characterized by locally aggressive behavior and late metastasis.

• Fibrosarcomas are seen most commonly on the gingival margin of the maxilla, between the upper canine tooth and the fourth premolar.

• Due to extensive tissue invasion, local recurrence is common, especially in tumors that cross the midline of the hard palate or are caudally located.


Treatment and Prognosis



• Wide surgical resection is the treatment of choice.

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Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Neoplasia of the Maxilla and Mandible

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